One frac technique involves an array of sliding sleeve valves that are actuated with dropped balls that get progressively larger as valves are opened in a bottom up direction within an interval of interest. Alternatively, the same size ball can be used to operate multiple sleeves. Each ball lands on a discrete seat to allow pressure to be built above the seated ball and that pressure is used to shift a sleeve to expose a series of frac ports. As each zone is treated in an interval through an open valve that valve is isolated when the next ball that is slightly larger is landed on the next sleeve in an uphole direction and the process is repeated. When the entire interval is treated, the balls and seats are milled out or alternatively production begins.
It is advantageous to hold the already shifted sleeves in the ports open position and in the past this has been done with a lock device. The lock can be used to lock the sleeve in the run in position and when defeated allow the sleeve to shift or the sleeve can have its shifted position locked. Illustrative examples of locking devices for shifting sleeves are: US2015/0152709; U.S. Pat. Nos. 7,455,118: 8,272,443: 8,220,555; US 2016/0290092; US2015/0211324 and US 2013/0248189. More noteworthy is U.S. Pat. No. 8,915,300 which has a protected interior sleeve for a valve so that cementing or treatment which can include debris can occur through the valve and beyond without fouling the track on which the shifting sleeve would then later have to move. The shifting sleeve has a lock ring with ratchets on opposing sides. The lock ring rides with the pressure actuated sleeve after access to the interior sleeve is provided with the breaking of a breakable member. The lock ring travels with the powered sleeve to another set of ratchet teeth which locks the interior sleeve in a shifted position.
The shortcoming of this design is the drift dimension of the innermost sleeve is reduced because the shifting sleeve that is between the outer housing and the inner stationary protective sleeve has to be protected during cementing and thereafter the frac pressure has to penetrate cement that has earlier filled the annulus. The use of a double sided lock ring also adds cost and operational complication to the design.
The present invention retains a shifted frac sleeve in an opened position using a ratchet pattern on the sleeve that comes into engagement with a lock ring that has a facing ratchet pattern as well as a tapered leading end that in the event of a force that would otherwise urge the sliding sleeve back to the closed position creates a wedging action off the surrounding housing that forces the lock ring against the sliding sleeve. The lock ring is loosely retained in a housing recess. After sleeve movement that puts a ratchet pattern in alignment with the lock ring it is movement in the reverse direction that forces the locking ratchet patterns together. These and other aspects of the present invention will be more readily apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawing while appreciating that the full scope of the invention is to be determined from the appended claims.